Police are investigating a letter a woman in Webster Groves, Missouri, received criticizing her family’s decision to post a “Black Lives Matter” sign in their yard in a predominantly white neighborhood.

Courtney Schaefer told KSDK she received the note in the mail last month after similar signage went missing around the neighborhood. Schaefer said the letter was addressed to “Resident” and included her address, which was written upside down.

“We, your neighbors, appreciate that you have strong political and social viewpoints and wish to communicate to others via your yard sign," Schaefer said the note read.